1. Field of the Invention
The invention generally relates to receivers for receiving scanning signals and, in particular, to an apparatus which receives signals having a predetermined time varying format allowing prediction of appropriate AGC levels such as a microwave landing system (MLS) receiver for receiving scanning signals provided by an MLS ground system.
2. Description of the Prior Art
The International Civil Aviation Organization (ICAO) has adopted a time reference scanning beam (TRSB) technique as the standard for civil microwave landing systems. MLS ground systems provide elevation (EL) and azimuth (AZ) scanning beams, each including a TO scan followed by a FRO scan, defining the area of coverage of the ground system. An MLS receiver located in an aircraft receives the EL scan and AZ scans and is able to determine the azimuth and elevation locations of the aircraft with respect to the ground system.
Since MLS receivers must operate in a time division multiplex mode in which the relative amplitudes of successive signals of interest may vary greatly, the receiver must adjust for anticipated amplitude levels prior to an anticipated detection. Specifically, the appropriate automatic gain control (AGC) voltage must be applied to the amplifier of the receiver prior to the anticipated detection of each angle function.